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Abstract:

We propose, by performing advanced
ab initio
electron transport calculations, an all-oxide composite
magnetic tunnel junction, within which both large tunneling magnetoresistance (TMR) and tunneling
electroresistance (TER) effects can coexist. The TMR originates from the symmetry-driven spin filtering
provided by an insulating
BaTiO
3
barrier to the electrons injected from the
SrRuO
3
electrodes. Following
recent theoretical suggestions, the TER effect is achieved by intercalating a thin insulating layer, here
SrTiO
3
, at one of the
SrRuO
3
=
BaTiO
3
interfaces. As the complex band structure of
SrTiO
3
has the same
symmetry as that of
BaTiO
3
, the inclusion of such an intercalated layer does not negatively alter the TMR
and in fact increases it. Crucially, the magnitude of the TER also scales with the thickness of the
SrTiO
3
layer. The
SrTiO
3
thickness becomes then a single control parameter for both the TMR and the TER
effect. This protocol offers a practical way to the fabrication of four-state memory cells